1. Field of the Invention
The present invention relates to a character segmentation device, a character segmentation method used thereby, and a program therefor. It relates in particular to a character recognition device for automatically reading characters from input image data.
2. Description of Related Art
Known character recognition devices of this type include devices for reading names and addresses, product serial numbers, etc. that have been written inside frames on postal items or preprinted forms. These character recognition devices employ a character segmentation device for extracting characters written or printed in character entry frames (hereinafter termed simply “character frames”) that have been preprinted in a color that will not vanish when an image of the region to be read is input. The configuration of a character segmentation device of this type is shown in FIG. 15.
The conventional character recognition device shown in FIG. 15 comprises image input part 21, character frame information input part 22, character frame detector 23, character frame information memory 24, character frame remover 25, character image output part 26 and controller 27.
For example, in the image processing device disclosed in JP 2000-354150 A, the means for detecting frames in the image data derived from a preprinted form comprises scanning the image in conjunction with a line memory, which is equivalent to extracting an image histogram, and identifying places where the histogram has a large cumulative value as corresponding to the position of a character frame. In this image processing device, the character frame removal means comprises extracting the image inside a character frame by using a masking unit to ignore those portions identified as corresponding to the character frame.
The use of a histogram for detecting character frames also features in the character frame detector disclosed in JP H08-007031 A and the image segmentation device and character recognition device disclosed in JP H08-287184 A. However, the use of a histogram sometimes results in erroneous detection of a character frame due to the influence of the character written or printed within the frame. This is mentioned in connection with the character segmentation device and character segmentation method disclosed in JP 2000-207490 A.
In the character segmentation device and character segmentation method disclosed in JP 2000-207490 A, the influence of characters is lessened by enhancing the histogram. However, if the character frame has a narrow line width or is printed faintly, the character frame image itself can end up being blurred if the image of the character frame in the input image is scanned at around 200 dots per inch.
A further problem encountered with the devices and methods mentioned above is erroneous detection of character frames when these frames are not present at sufficiently high quality in the input image. Moreover, because each character frame is detected in a single processing cycle without any alteration of the input size, given that there are cases in which the quality of a character frame is poor, it is not feasible to compress the image size in order to improve processing speed. As a result, the speed/performance ratio of these conventional devices and methods is poor.